1. Field of the Invention
The present invention relates to a transmission device between an input drive shaft and an output shaft, such as the shaft for driving the wheels of a travelling machine.
2. Description of the Related Art
It relates more particularly to a transmission device comprising a housing, inside which are placed at least partially a reduction gear mechanism and a progressive cone clutch mechanism, the said reduction gear mechanism comprising a driving member engaged with a driven member, the driven member of the reduction gear mechanism being formed by a gearwheel mounted so as to rotate freely on the output shaft and able to be coupled to/uncoupled from the said output shaft by means of the two friction cones of the clutch mechanism, the said cones being placed coaxial to the axial bore of the gearwheel and capable of coming, under the action of a control device, into bearing contact with a conical bearing surface of the gearwheel.
Such transmission devices are well known to those versed in this art. However, the drawback of such a solution lies in the fact that, hitherto, the portion of the wheel furnished with gear teeth and the cones are placed coaxially and concentrically, the face of the gearwheel opposite to the gear teeth being furnished with conical bearing surfaces.
Accordingly, the dimension of the cones, in particular the circumference of the circles forming the base and the truncated apex of the cone, is limited to the diameter of the gearwheel. The result of this is a limitation in the torque that can be transmitted.